Prior Art
FIG. 5 is a schematical drawing of a conventional type atomizer mechanism for sprinkling chemicals.
In this figure, the reference numeral 10 designates a pulse-jet engine, and reference numeral 20 designates a combustible air-fuel mixture supply unit. Reference numeral 40A designates an engine starter, and reference numeral 60 designates is a chemical supply unit.
When the combustible air-fuel mixture containing the air and fuel (gasoline) is exploded by means of a glow coil 12 for ignition in a combustion chamber 11 of the pulse-jet engine 10, chemicals such as aqueous insecticide supplied from the chemical supply unit 60 are atomized by the use of high speed gas generated by the explosion. Also, the combustible air-fuel mixture supply unit 20 supplies the combustible air-fuel mixture to the combustion chamber 11 of the pulse-jet engine 10.
Describing the conventional mechanism more concretely, the pulse-jet engine 10 comprises a combustion chamber 11 as described above, an engine exhaust cylinder 13, for discharging combustion gas at high speed as a high temperature gas, through a throttling area from the combustion chamber 11, an outer cylinder 14 to cover the outer surface of the engine exhaust cylinder 13, and a cooling air suction cylinder 15 for sucking cooling air from external atmosphere and for guiding it into the outer cylinder 14.
Also, the combustible air-fuel mixture supply unit 20 comprises a precombustion chamber 21, a collecting valve 25 and a carburetor 31.
The precombustion chamber 21 is communicated with the combustion chamber 11 of the pulse-jet engine 10 through a communication pipe 22 and supplies the combustible air-fuel mixture generated in the carburetor to said combustion chamber 11.
The carburetor 31 mixes the air and the fuel (gasoline) in a predetermined ratio and atomizes the mixture. It sucks the fuel from a fuel tank 51 through a fuel supply pipe 52 using a pressure wave (impulse) from the precombustion chamber 21 supplied through a pressure pipe 23, atomizes the fuel and injects into the precombustion chamber 21 through a collecting valve 25.
The collecting valve 25 has a valve of the structure already known and comprises a valve seat 27, made of aluminum and provided with a plurality of penetrating holes positioned along a circle at a predetermined spacing, and a flexible diaphragm 26, made of stainless steel and provided with plate valves, the plate valves being elastically deformed by pressure change in the precombustion chamber 21 and capable of opening or closing each of the penetrating holes of the valve seat 27. That is, when the pressure in the precombustion chamber 21 is increased, the flexible diaphragm 26 of the collecting valve 25 is deformed, and the plate valves close the penetrating holes of the valve seat 27 (valve closed). When the pressure in the precombustion chamber 21 is decreased, the diaphragm 26 of the collecting valve 25 is deformed, and the plate valves open the penetrating holes of the valve seat (valve opened).
The engine starter 40A starts the pulse-jet engine 10 and is normally designed to be of a pneumatic pressure type. More concretely, the engine starter 40A comprises a manual air pressure pump (not shown), an ignition plug 45 for igniting the combustible air-fuel mixture, causing it to explode in the precombustion chamber 21, and an ignition coil 46 to provide power for the plug 45.
A prime pump 41A pressurizes fuel from the fuel tank 51 as it is sucked through pipe 43, carburetor 31 and fuel pipe 52 by manual operation and can inject it into an air passage 33 of the carburetor, via a pipe 42. The air pressure pump, by manual operation discharges air from the right inner wall of the precombustion chamber 21 in FIG. 5 through a pulse pressure pipe 63 and a ventilation pipe 29 as further described below and can atomize the fuel supplied through the collecting valve 25.
By manually operating the prime pump 41A and the air pressure pump as described above, fuel can be supplied into the precombustion chamber 21 as atomized gas through the air passage 33 of the carburetor 31 and the collecting valve 25. The atomized fuel is ignited by the plug 45 heated by the ignition coil 46, and as the result, the engine 10 is started. Then, the glow coil 12 is heated up, and the carburetor 31 repeatedly injects the fuel by pulse pressure through the pressure pipe 23. Thus, normal operation of the pulse-jet engine 10 is performed.
On the other hand, the chemical supply unit 60 comprises a tank 61, a supply pipe 62, the pulse pressure pipe 63, and a chemical discharger 64. Pressurized by the pulse pressure in the precombustion chamber 21 in normal operation, the chemical (such as aqueous insecticide) is injected and supplied into the engine exhaust cylinder 13 from the chemical discharger 64. The chemical injected from the chemical discharger 64 is gasified and cooled down by external air inside a cooling chamber 16 formed in the outer cylinder 14. As the result, the chemical is turned to fumes containing particles of size 1 to 0.5 .mu.m or less.
Among users of the atomizer mechanism as described above, there are strong demands to make it easier to handle, while the hardest bottleneck to meeting such demands is the starting of the pulse-jet engine 10.
Specifically, the engine 10 is started by manual operation of the air pressure pump and the prime pump 41A connected to the ventilation pipe 29, and the start-up is sometimes not smooth because the air and the fuel are not mixed at a predetermined ratio and the fuel often becomes too dense due to inadequate stroke or speed of the air pressure pump.
To prevent excessive condensation of the fuel, a compressor is connected to the ventilation pipe 29 instead of the air pressure pump and the air, under a predetermined pressure, is sent in a horizontal direction at a predetermined flow rate into the precombustion chamber 21. With such an arrangement, however, the fuel injected into the carburetor 31 by the prime pump 41A often attaches to on the collecting valve 25 in large quantity when it passes through the valve 25, and the fuel is supplied to the precombustion chamber 21 in a so-called dripping state from the collecting valve 25. As the result, the plug 45 is often moistened and is unable to start. Because the holding position of the entire system varies according to the operator, it is very difficult to start in a rapid and reliable manner.